I would go to
www.wizards.com/eberron and read Keith Baker's Dragonshard articles, to get a glimpse of what the world is like. It will leave you with some questions and holes in your knowledge that only the Eberron Core book can fill in, but it may whet your appetite and see if you want more or not.
The things I like about Eberron:
--Low level good NPCs, mid to high level Neutral NPCs, some high-level evil NPCs in the default world, so that the PCs are often the only ones who can possibly do something about a catastrophic action.
--Many slight mechanics changes and conceits to make the world a more pulp/noir place, e.g. full functional evil clerics of good causes, a recent catastrophic war that the world is JUST healing from, a couple of metropolis cities ripe for urban intrigue, but plenty of untamed wildlands and ruined areas
-- not one but TWO nations of "monsters"
--plenty of environments for pirate games, lost world games, "playing the enemy/underdog" games, apocalyptic landscape games, etc.
--few to no real-world analogues for cultures, religions, etc.
What I like about the Realms:
--The tolkienistic heroism elements in the background
--The clash of medieval european, asiatic, egyptian, etc. cultures
--The ancient pockets of evil and godlike magic waiting to be encountered
--The absolutely prevailing years of history that are available for this setting.
Take your pick, but I would definitely go wander WotC's Eberron boards before I took the plunge. It will either get you going, or turn you off, and you'll make up your mind cleanly.